Handle escapes in string literals.

frog/leg/scanner/scanner.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 interface Scanner {
   Token tokenize();
 }
 
 /**
  * Common base class for a Dart scanner.
@@ skipping 611 matching lines @@
         return next;
       }
     }
     if (raw) {
       return tokenizeSingleLineRawString(next, q, start);
     } else {
       return tokenizeSingleLineString(next, q, start);
     }
   }
 
+  static bool isHexDigit(int character) {
+    if ($0 <= character && character <= $9) return true;
+    character |= 0x20;
+    return ($a <= character && character <= $f);
+  }
+
   int tokenizeSingleLineString(int next, int q1, int start) {
-    while (next !== $EOF) {
+    loop: while (next !== $EOF) {
       if (next === q1) {
         appendByteStringToken(STRING_INFO, utf8String(start, 0));
         return advance();
       } else if (next === $BACKSLASH) {
         next = advance();
-        if (next === $EOF) {
+        if (next === $EOF || next === $LF || next === $CR) {
           throw new MalformedInputException(charOffset);
         }
+        switch (next) {
+          case $u:
+            next = advance();
+            bool isBracketed = false;
+            int maxLength = 4;
+            if (next === $OPEN_CURLY_BRACKET) {
+              isBracketed = true;
+              maxLength = 7;
+              next = advance();
+            }
+            int startOffset = charOffset;
+            int unicodePoint = 0;
+            int length = 0;
+            while (length < maxLength && isHexDigit(next)) {
+              int digit = next <= $9 ? next - 0x30 : (next | 0x20) - ($a - 10);
+              unicodePoint = unicodePoint * 16 + digit;
+              length += 1;
+              next = advance();
+            }
+            if (isBracketed) {
+              if (length === 0) {
+                throw new MalformedInputException(startOffset);
+              }
+              if (next !== $CLOSE_CURLY_BRACKET) {
+                throw new MalformedInputException(charOffset);
+              }
+              next = advance();
+            } else if (length != 4) {
+              throw new MalformedInputException(startOffset + length);
+            }
+            if ((0xD800 <= unicodePoint && unicodePoint <= 0xDFFF) ||
+                unicodePoint > 0x10ffff) {
+              // Don't allow invalid code points in strings.
+              throw new MalformedInputException(startOffset);
+            }
+            // TODO(lrn): This should be just "continue", but the VM is bugged.
+            continue loop;
+          case $x:
+            for (int i = 0; i < 2; i++) {
+              next = advance();
+              if (!isHexDigit(next)) {
+                throw new MalformedInputException(charOffset);
+              }
+            }
+            break;
+          default:
+            // All other escapes are trivially valid.
+        }
       } else if (next === $$) {
         beginToken();
         next = advance();
         if (next === $OPEN_CURLY_BRACKET) {
           next = tokenizeInterpolatedExpression(next, start);
         } else {
           next = tokenizeInterpolatedIdentifier(next, start);
         }
         start = byteOffset;
         continue;
@@ skipping 57 matching lines @@
     }
     return next;
   }
 }
 
 class MalformedInputException {
   final message;
   MalformedInputException(this.message);
   toString() => message.toString();
 }